The objective of this epidemiologic study is to identify new risk factors for cardiac abnormalities which may result from interactions of multiple teratogenic agents or enhancements of fetal damage by non-teratogenic substances. Index cases will be 750 infants with severe congenital heart disease identified over a 3-year period through the Regional Pediatric Cardiology Services in Baltimore and Washington. Control infants will be chosen at random from the births occurring in area hospitals served by the Cardiology Centers. Information will be obtained by home interviews. A pre-coded questionnaire administered to the mother will record details of pre and post-conception exposures to drugs, smoking, alcohol and caffeine. Home environmental exposures caused by heating and cooking fuels, and maintenance activities (paints, insecticides) and crafts and hobbies (solvents, laquer) will be noted. Occupational histories of mother and father will be examined by industry, type of job, and potential teratogen. Analyses by multiple logistic regression will seek to elucidate additive and interactive effects of the various exposures, after adjustment for confounding variables. Because the multifactorial origin of congenital malformations is widely accepted, a summation or enhancement of environmental insults in the pathogenesis of congenital heart disease is a reasonable possibility, worthy of investigation.